Aluminum bronze alloy having improved wear resistance by the addition of cobalt and manganese



nited States Patent '0 ALUMINUM BRONZE ALLOY HAVING IM'PROVED WEAR RESISTANCE BY THE ADDITION OF CO- BALT AND MANGANESE John F. Klement, Milwaukee, Wis., assiguor to Ampco .Metal, Inc., Milwaukee, Wis., a corporation of Wiscon- No Drawing. Filed Nov. 21, 1958, Ser. No.-775,351

6 Claims. (Cl. 75-161) Patented Apr. 11, 1961 A specific illustration of the composition of the alloy falling within the above range is as follows in weight percent:

The alloy of the invention has greatly improved wear resistance over that of an ordinary aluminum bronze alloy. A comparison of the wear resistance of the alloy of the invention to that of a conventional aluminum This invention relates to an alumlnum bronze alloy bronze alloy 1s illustrated in the following table:

Wear Rate in A110 Hard- Grams per Mating No. Ou Al .Fe Co Mn ness 1,000 in. kg. of Alloy Frictional Work 1 81.71 14. 0s 4. 21 38R 0.00508 18-8 Stainless Steel. 2 7s. 53 14. 24 7. 23 391cc 0. 00546 Do. a s1. 50 13. 95 4.55 sane 0. 00544 Do. 4 73. 93 15. 10 5. 01 3. 1s 2. 7s 39Rc 0. 00371 Do.

and more particularly to an aluminum bronze alloy having improved toughness and wear resistance.

Aluminum bronze alloys have for years been used as dies for forming and drawing operations fora large group of sheet and plate alloys, such as stainless steel, aluminum, nickel, titanium, mild steel and some copper base alloys. Aluminum bronze alloys used in die applications possess the properties of good corrosion resistance, wear resistance and non-galling against many wrought materials.

The aluminum bronze alloys which in the past have shown the optimum properties for deep drawing dies are those that contain approximately 14% aluminum, a small amount of iron and the balance copper. An alloy of this type has good corrosion resistance and non-galling properties. However, under heavy use in die application, it wears undesirably fast so that close dimensional tolerances cannot be maintained because of the wear that occurs on the die surface.

The present invention is directed to an aluminum bronze alloy which has the corrosion resistance and the non-galling properties characteristic of aluminum bronze alloys but has greatly improved wear resistance and toughness.

The aluminum bronze alloy of the invention has high uniform hardness, good toughness and excellent wear resistance. This is accomplished by the addition of small amounts of cobalt and manganese to the alloy which substantially eliminates the tendency of the alloy to form the eutectoid. The addition, of cobalt and manganese also makes the alloy more homogeneous in the distribution of the metallurgical phases and compounds during solidification and heat treatment and also promotes uniform controlled grain size.

' The alloy of the invention has the following general composition by weight:

Aluminum 13.016.0%. Iron 3 .06.Q% Cobalt In a ratio of .07 to The wear test results of the above table were obtained on a rolling-slip friction device, such as an Amsler wear test machine. In these tests, the aluminum bronze alloy cylindrical test specimens were subjected to rolling and sliding motions against stainless steel cylinders with an applied compressive stress of 31,500 p.s.i. on the specimens. The test specimens 1', 2 audit, in the table, contain only iron and aluminum in combination with copper and have a substantially lower resistance to wear than specimen number 4 which falls within the scope of the present invention. The'increase in wear resistance due to the addition of cobalt and manganese to aluminum bronzeis most significant since the hardness of all specimens is substantially the same.

vWith the cobalt and manganese addition to aluminum bronze alloys, the wear rate of the alloy against stainless type steels is in the range of 0.0025 to 0.0055 gram per one thousand meter kilogram (m.kg.) frictional workas measured by Amsler wear testing machine. In addition, the alloy has a hardness in the range of 25 Rockwell C to 55 Rockwell C, depending on the specific aluminum,- cobalt and manganese contents in the alloy.

In addition to substantially increasing the wear resistance of the alloy, the addition of cobalt and manganese also substantially eliminates the tendency for eutectoid formation in the alloy. The eutectoid structure consists of alpha phase plus gamma two phase formed from the transformation-decomposition of the beta phase. 'This transformation occurs at temperatures below 1050 F. in aluminum bronze alloys and the resultant eutectoid structure is brittle and possesses low ductility and poor machinability. However, with the alloy of the invention, it is possible to heat the alloy for a period up to three to five hours without formation of the embrittling eutectoid. In contrast to this, an ordinary aluminum bronze die alloy would be so embrittled by a heat treatment for this length of time that any machining operation could only be done with great difiiculty.

It is essential that the cobalt and manganese be maintained within the limits of 0.07 to 0.31 part by weight per part of aluminum. If the cobalt or manganese content falls below this ratio the effect of the addition on the wear resistance is negligible. If the cobalt content is increased above the stated ratio, the efiect of the cobalt in increasing the wear resistance is reversed. In addipercentage of the pre-alloy and copper.

tion a cobalt content substantially above the stated ratio increases the afiinity of the alloy for stainless steel and thereby reduces its effectiveness as a deep drawing die. It is believed that the reason for this affinity-is that the cobaltis similar in properties to the nickel in the stainless steel and the high cobalt intermetallic compounds tend to pick-up or gall the stainless steel.

If the manganese content is increased above 0.31 part per part of aluminum, the manganese also produces a reverse effect on the wear resistance of the alloy and the wear resistance decreases. Furthermore, if more than-031 part of manganese per part of aluminum is used, there'is a tendency to obtain the ,8 phase instead of the desired 72 phase. Therefore it is necessary to add additional aluminum, over 16%, with higher man ganese contents in order to retain the 72 phase. This additional aluminum results in crystalline weakness and brittleness. A manganese content above the stated ratio also increases the grain size of the alloywhich is undesirable.

As manganese tends to reduce the thermal conductivity of the alloy, excessive amounts of manganese over 0.31 part per part of aluminum should be avoided. A decrease in thermal'conductivity brought about by a high manganese content will reduce the rate of heat dissipation from the die surface, thereby increasing the temperature of the die surface. A high temperature on the die suror any of the inert gases. The dry type deoxidizers are added in quantities of approximately 4 ounces per 100 pounds of metal, and the gas type deoxidizers are passed either through or over the molten metal for a period of five minutes. Removal of the oxide particles is of particular importance because of their abrasive and adverse affect on the wear-resistant properties of the alloy.

To establish complete uniformity of the microstructure and hardness the alloy is heat treated at an elevated temperature in the temperature range of 1050 F. to 1400 R, such as about 1150 F. Small castings of sim* ple shapes of this alloy can beplaced directly into the mone-halfhour per inch of section thickness greater than face'is apt to decompose or destroy the die lubricant theresult that galling occurs. Furthermore a decrease in thermal conductivity results in a decrease in the rate of heat dissipation from-the whole mass of the die, thereby increasing the temperature of the die to a point where the generally non-ductile die may crack.

The alloy of the invention containing about 15% aluminum, 5% iron, 3.2% cobalt, 2.8% manganese and the balance being substantially copper, can be cast either statically or centrifugally to produce a fine grained tough structure having a tensile strength of about 105,000 p.s.i., a yield strength of 75,000 p.s.i., an elongation in two inches of 1% and a Rockwell C hardness of 39.-

The metallo'graphic structure of the above alloy consists essentially of gamma two phase which is uniformly distributed in a matrix of beta. An intermetallic compound composed of iron, aluminum, copper, cobalt and manganese exists in small particles of'uniform size and shape. 'Because of the method of casting and the -'i.n oculant used, the intermetallic compound is uniformly distributed throughout the'cast section. t In order to obtain optimum properties, the metalsused for the alloy-should be of high quality. Electrolytic or wrought fire'refined copper, high purity aluminum, low' carbon iron and high purity cobalt and manganese are preferred to' be used. It has also been found that the best method of obtaining the desired uniformity in the alloy is by using a double melting procedure whereby a pre-alloy is made. The most satisfactory'pre-alloy is one that has approximately 45% aluminum, copper, iron, 10% manganese and 10% cobalt. The melting procedure employed in making the prealloy is such that some copper, along with the iron, manganese and cobalt, is placed into the crucible and melting begun. When the copper starts to melt, the iron and other additives are slowly dissolved into the copper during that. period when aluminum is added to form-an exothermic reaction which helps to dissolve" the higher melting point cobalt :and .manganese additions. Thisp're alloy is then cast into ingot form andis' ready to use for thefinal alloy. o

The final alloy is made by intermixing a predetermined A deoxidizer is added tothis alloy in the molten state in the furnace to purge themetal of oxides and soluble gases. These deoxidizers can .include'the compounds of-boron, phosphorus, magnesium and lithium. Deoxi dizers, of the, gas type can also be used. This can include volatile chlorides "depending on the future application of the part.

one inch, up to a maximum of two and one-half hours at temperature.

After the required soaking time at the elevated temperature, the alloy is cooled at a rate faster than about 20 F.. per hour per one inch of section thickness. This rate is conveniently obtained by fan air cooling.

Internal stresses created within castings during machining or other finishing operations, during weldments or from metal overlays on base metals, are usually removed These stresses are removed by a stress relief heat treatment. The usual commercial aluminum bronze alloys cannot generally be stress relieved at a temperature in the range of 650 F. to 1050 F. due to eutectoid formation that I temperature.

, stress relieved within the temperature range of 650 F.

to 1050 F. without embrittlement due to the excessive eutectoid structure. An optimum stress relief temperature for the present alloy, based on the severity of the internal stresses and geometry of the article, can be selected in the range of 650 F. to 1050 F. to obtain a reasonable holding time in the furnace, such as one to two hours per 2' inches of section, and to prevent distortions and micro stresses during cooling. The article is then cooled to room temperature.

,, T The alloy can be used to produce articles for wear resistantapplications in drawing and forming operations.

The articles may take the form of deep drawing dies, hold down dies,- wear guides, forming rolls, skids, slides, etc. The alloy can also be extruded into Weld rods or Weld'wire. The alloy in the form of coated or uncoated weld rod can be overlaid on a base metal by metal spraying or other welding methods, such as hell-arc, metalarc, carbon arc, etc. to obtain a corrosion resistant wear surface. The metal overlay can be given a stress relief treatment at temperatures in the range of 650 F. to

1150 F. and cooled to room temperature.

T Itxhas been found that the addition of cobalt and manganese to the copper-aluminum-iron alloys to be used as die materials greatly improves the toughness-and wear resistanceofthealloy and substantially eliminates the tendency for eutectoid embrittlement.

Thisapplication is a continuation-in-part of application Serial No. 705,483, filed December 27, 1958, now abandoned, and entitled Aluminum Bronze Alloy Having Improved Wear Resistance by the Addition of Cobalt and Manganese.

Various modes ofcarrying out the invention are contemplated as being within the scope of the following U claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. An aluminum bronze alloy, consisting essentially by weight of 13.0% to 16.0% aluminum, 3.0% to 6.0% iron, cobalt in a ratio of 0.07 to 0.31 part per part of aluminum, manganese in a ratio of 0.07 to 0.31 part per part of aluminum and the balance being essentially copper, said alloy being characterized by having excellent corrosion resistance and having improved toughness and wear resistance.

2. An aluminum bronze alloy, consisting essentially by weight of 13.0% to 16.0% aluminum, 3.0% to 6.0% iron, cobalt in a ratio of 0.07 to 0.31 part per part of aluminum, manganese in a ratio of 0.07 to 0.31 part per part of aluminum and the balance being essentially copper, said alloy having a wear rate in the range of 0.0025 to 0.0055 gram per one thousand meter kilograms of frictional work as measured on a rolling slip wear testing machine against 18-8 stainless steel.

3. An aluminum bronze alloy, consisting essentially by weight of 13.0% to 16.0% aluminum, 3.0% to 6.0% iron, cobalt in a ratio of 0.07 to 0.31 part per part of aluminum, manganese in a ratio of 0.07 to 0.31 part per part of aluminum and the balance being essentially copper, said alloy having a wear rate in the range of 0.0025 to 0.0055 gram per one thousand meter kilograms of frictional work as measured on a rolling-slip wear testing machine against 18-8 stainless steel and having a hardness in the range of 25 to Rockwell C.

4. A drawing die characterized by having excellent corrosion resistance, a hardness in the range of 25 to 55 Rockwell C and a wear rate in therange of 0.0025 to 0.0055 gram per 1000 meter kilograms of frictional work as measured by a rolling-slip wear testing machine, said die being fabricated from an aluminum bronze alloy consisting essentially byweight of 13.0% to 16.0% aluminum, 3.0% to 6.0% iron, cobalt in a ratio of 0.07 to 0.31 part per part of aluminum, manganese in a ratio of 0.07 to 0.31 part per part of aluminurmand the balance being essentially copper.

5. An aluminum bronze welding electrode consisting essentially by weight of 13.0% to 16.0% aluminum, 3.0% to 6.0% iron, cobalt in a ratio of 0.07 to 0.31 part per part of aluminum, manganese in a ratio of 0.07 to 0.31 part per part of aluminum, and the balance being essentially copper.

6. An aluminum bronze alloy having improved toughness and wear resistance, consisting essentially of 15.10% aluminum, 5.01% iron, 3.18% cobalt, 2.78% manganese and 73.93% copper.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,430 Mass July 9, 1935 2,210,671 Kelly 2 Aug. 6, 1940 2,430,419 Edens Nov. 4, 1947 

1. AN ALUMINUM BRONZE ALLOY, CONSISTING ESSENTIALLY BY WEIGHT OF 13.0% TO 16.0% ALUMINUM, 3.0* TO 6.0% IRON, COBALT IN A RATIO OF 0.07 TO 0.31 PART PER PART OF ALUMINUM, MANGANESE IN A RATIO OF 0.07 TO 0.31 PARTS PER PART OF ALUMINUM AND THE BALANCE BEING ESSENTIALLY COPPER, SAID ALLOY BEING CHARACTERIZED BY HAVING EXCELLENT CORROSION RESISTANCE AND HAVING IMPROVED TOUGHNESS AND WEAR RESISTANCE. 